Structural defects to skeletal muscle range from the relatively benign to the profoundly debilitating. Malformations of this tissue may evolve as a result of a developmental abnormality or as a consequence of traumatic injury. Regardless of the source, structural defects to the skeletal muscle can affect a patient on a number of different levels. For example, a structural defect to the musculature of the face may have a minor impact on the ability of a patient to survive. However, even a minor cosmetic defect can have profound psychological implications. Defects to the muscles of the axial skeleton can limit mobility and thereby reduce quality of life. An overlooked area of craniofacial repair is the field of tissue engineering skeletal muscle prostheses. The objective of this proposal is to engineer a biological implant that can be used to restore structure and function to dysfunctional skeletal muscle. Ideally, such prosthesis should be composed of skeletal muscle myotubes arranged in a pattern equivalent to intact muscle. The engineered tissue should be malleable so that it is possible to sculpt the tissue to restore the contours of missing or damaged muscle. In the preliminary data section of this proposal, we present evidence that we have successfully constructed a multilayered culture of skeletal myocytes derived from neonatal satellite cells that exhibit a three dimensional, tissue-like pattern of organization. We propose to build upon these preliminary experiments to develop a three-dimensional skeletal muscle construct that is pre-adapted to the in vivo environment and is suitable for transplantation and repair of a skeletal muscle defect. The Specific Aims of this proposal are: 1). To produce skeletal muscle constructs that mimic the structure and function of adult skeletal muscle and are pre-adapted to the in vivo environment. 2). To characterize the engineered three-dimensional skeletal muscle constructs with respect to intact tissue using morphological, biochemical, molecular and physiological techniques.